Call-for-service circuits of communication switching marker



June 24, 1969 J. R. VANDE WEGE CALL-FOR-SERVICE CIRCUITS OFCOMMUNICATION SWITCHING MARKER BY wg;

`lune 24, 1969 J. R. VANDE WEGE 3,452,159

cALL-FoR-sERv1cE CIRCUITSOF coMMuNxcATIoN swITcHING MARKER June 24, 1969J. R. VANDE WEGE CALL-FOR-SERVICE CIRCUITS OI COMMUNICATION SWITCHINGMARKER Filed Dec. 29, 1965 sheet 3 l of 15 Au u 'l STAGE, QsTAGE iSTAGE) DAS l 1 las I5\ 2A Y i1 l f- I] Q In |2 L I0 Y XII I2 (2C I L`*`l DSA |AL DSA MARKER MARKER IA' i IMs IB T fl LINES A "BA' i2. ANDsTAGE sTAGEw TRuNKs L A I Y ma" j STAGE RJI L J I I l f ,I A r I I Y I`l Jl` CII "BC/l RJN l sTAGE sTAGE l I l SWITCH SWITCH ZIAL swITCH GROUPMARKER MARKER *T* zIA IMS 2IEI L 30 "M" u v* "W"- u" muh m T I I ICOMMON COMMON LOGIC LOGIC LOGIC I SIA 3IC BIB RN Q j L L @33 MEMORYMEMORY FIG. 3 32A @IMG N 32B CONTROL GROUP `Fume 24, 1969 J. R. VANDEWEGE CALL-FOR-SERVICE CIRCUITS OF COMMUNICATION SW'ICHING MARKER 4 of l5sheet Filed Dec. 29, 1965 v n:E E

June 24, 1969 .1.R. VANDE WEGE 3,452,159

CALL-FOR-SERVICE CIRCUITS OF COMMUNICATION SWITCHING MARKER Filed Dec.29, 1965 sheet 5 of 15 DSA TRUNK FIG. 5 DIH FRONT TERMINATION SWITCHMATRIX REAR TERMINATION SWITCH MATRIX June 24, i969 .1. R. VANDE WEGE3,452J59 CALL-FOR-SERVICE CIRCUITS OF COMMUNICATION SWITCHING MARKERFiled Dec. 29, 1965 Sheet of 15 (TX 51 Rvi g 'TLKI T1 I PMSA- T I I 5T|R-f sTKF/' I I F I I 1 I l I TI] I l I I IERl] `lune 24, 1969 3,452,l59

CALL-FOR-SERVICE'CIRCUITS OF COMMUNICATION SWITCHING MARKER J. R. VANDEWEGE Filed Dec. 29, 1965 Sheet J. R. VANDE WEGE `une 24, 1969cALL-FoR-SERVICE CIRCUITS oF COMMUNICATION swITcHING MARKER Filed Dec.29, 1965 FIG.8

June 24, 1969 J. R. VANDE WEGE CALL-FOR-SERVICE CIRCUITS OF COMMUNICTIONSWITCHING MARKER F'iled Dec. 29, 1965 sheet 9 of 15 1SBF PB l RPBC JALB9m.

DPF 9SF"% QWST ssp RF Lf @i3 @LC LH. as

soBF oso 9TK\ Il eLRc QTKVQ,l v HG STK LSTK POSITION CIRCUIT MN @MoN 'STK swsT @MON HINT JLFG I) v5 H' FIG. 9

PcFsP PCFS June 24, 1969 J. R. VANDE WEGE CALIrVOR SERVICE CIRCUITS OICOMMUNICATION SWTTCHING MARKER Sheet Filed Dec. 29. 1965 `lune 24, 1969J. R. VANDE WEGE 3,452fl59 CALLI"ORSERVICE CIRCUITS Ol'1 COMMUNICATIONSWITCHING MARKER Filed Dec. 29. 1955 l sheet or 15 |oPRs/\ loPRzfw 5 f f"IGM POSTION Il /IOPR4 l IOPR|7 l CIRCUIT l I *"FII B l SWST HINT 2GOKIIIj-I lib@ PM E @f-s cLAss SPE I POSITION CLASS CONDITION KEYS BILAMPS- T HKS? IICK CCB CO4 I/ i/ f s ma ALIA ICPITP lo-Hl "T- af-KigaPRIoRlT-Ir I :@/3

l June 24, 1969 J. R. VANDE WEGE 3,42,159

cALL-FoRsEMv1c CIRCUITS on COMMUNICATION sw'ITcHIMG MARKER Filed Dec.29, 1965 sheet f3 of 15 TPIII PLAIII TP LEADS PLA555 PLA LEADS CALLPARITY I I I I I PRIORITY SCANNER lOl TO MARKER B MARKER `une 24,1969 1. R. VANDE WEGE' 3,4525'9 CALL-FOR-SERVICE CIRCUITS OFCOMMUNICATION SWITCHING MARKER Sheet Filed Dec. 29, 1965 HBC502 mi N;

HAB554 PABHI sheet I4Z of 15 J. R. VANDE WEGE `unnie 24, 1969CALL-FOR-SERVICE CIRCUITS Ol" COMMUNICATION SWITCHING MARKER Filed Dec.29, 1965,

`Fune 24, 1969 J. R. VANDE WEGE 3,452,159 v CALL-FORSERVICE CIRCUITS OFCOMMUNICATION SWITCHING MARKER Filed Dec. 29. 1965 sheet /5 of 15 MARKERIA ARKER IE 1502 CFS y, ISPA l |5PB M SCFS l j i SCFS'B SS B l; l Q |503'L T l A I/A 1 |504 PAR-Eq Il l'\ I I C\ /C ,"1 I l f E 4|. l i, D\ l /Dl\ PAR *5l* TRJIJlE l V sx1 RECORDER I I scFs\ i CFS\ l I *Eo i512 I ssPARE-(TA) nlMs II I PARITY CHECK L FIG. l5

n FIG. I6 I2 I3 I4 FIG. I7

United States Patent O m 3,452,159 CALL-FOR-SERVI'CE CIRCUITS 0FCOMMUNICA- TION SWITCHING MARKER John R. Vande Wege, Glen Ellyn, Ill.,assignor to Automatic Electric Laboratories, Inc., Northlake, Ill., acorporation of Delaware Filed Dec. 29, 1965, Ser. No. 517,226 Int. Cl.H04m 3/64 U.S. Cl. 179-27 8 Claims ABSTRACT OF THE DISCLOSURE Switchingequipment selectively connects trunk circuits to operator positions.Trunk circuits calling for service have class and priority information.The marker supplies blanking potentials to mask the call-for-servicerequests of all but one class and 4priority at a time. When the trunkcircuit is connected to an operator position, the class and priorityinformation is forwarded via a time division path for display. Themarker is arranged to have a sequence of operations which is similar forservice requests from the operator positions and from the trunkcircuits.

This invention relates to a communication switching marker, and moreparticularly to a class of service marking arrangement.

One object of the invention is to provide a simple and effectivearrangement to mark trunks terminating on a switching network so thatcalls can be processed in accordance with class of service informationsuch as priority or operator class of call information.

According to one feature of the invention a plurality of class markingleads are connected in common between the marker and all of the trunkcircuits, and each trunk circuit is provided with an arrangement to opena connection between one of the class marking leads corresponding toclass of service information for the call and a calling conductor in thetrunk. A call for service signal comprises connecting a given source ofpotential to the calling conductor in the trunk, this conductor beingconnected via an identification network into an identification selectionarrangement in the marker. The marker in serving trunk calls for serviceoperates a scanner to place a different potential on the one classmarking conductor corresponding to the class of service to be served;this being the conductor which is disconnected from the callingconductor in all trunks having calls of that class of service. Thus thissecond potential is applied to the calling conductor of all trunksexcept those of the class of service selected by the marker andeffectively blanks the call signals in all of the other trunks. Forexample the call signal may be a negative potential supplied viaresistance to the calling conductor, and the blanking potentialconnected by the marker to the class conductor for the selected class ofservice may be ground potential.

Another feature relates to the arrangement of the sequence control inthe marker such that calls from trunk circuits terminating one side of aswitching network are processed with a given sequence of operations, andcalls from circuits terminating at the other side of the network areprocessed with substantially the same Isequence of operation. Forexample, in a network having trunk circuits terminating one side andlink circuits for operator positions terminating at the other side, thenormal sequence is for calls originating at trunks being extended to theoperator link circuit. The marker is arranged so that in a switchboardmode, calls originated -by operators are processed with substantiallythe same sequence of operations as calls originating at the trunks. Thisis accomplished by responding to a switchboard call for service to markall idle trunks as though they were calling for service, and to3,452,159 Patented June 24, 1969 mark only the calling operatorpositions as idle. The call is then processed to select one of thetrunks which has the call potential appearing on its call conductor andto extend it to a position which appears marked idle. Thus, the callingposition is connected to an idle trunk.

The above-mentioned and other objects and features of this invention andthe manner of attaining them will become more apparent, and theinvention itself will be best understood, by reference to the followingdescription of an embodiment of the invention taken in conjunction withthe accompanying drawings comprising FIGS. 1 to 17 wherein;

FIGS. 1 and 2 comprise a symbolic diagram of a dial service assistancetrunk and operator position group with a connecting switching network;

FIG. 3 is a block diagram of a system incorporating the arrangement ofFIGS. 1 and 2;

FIG. 4 is a diagram of the switching network used in the arrangement ofFIGS. 1 and 2 showing particularly the pull conductors and operatewindings of the crosspoint relays;

FIGS. 5-14 comprise a block and schematic diagram of the dial serviceassistance group shown symbolically in FIGS. 1 and 2;

FIG. 15 is a schematic and functional block diagram of a parity checkarrangement;

FIG. 16 shows how FIGS. 1 and 2 are to be arranged; and

FIG. 17 shows how FIGS. 5-14 are to be arranged.

The following references are of interest with respect to thecommunication switching system in which this invention is incorporatedand features thereof:

(1) Technical Bulletin 950-330` entitled, Autovon Switch, published byAutomatic Electric Company, 1964.

("2) U.S. patent application Ser. No. 450,275, filed Apr. 23, 1965, nowPatent No. 3,328,534 for Communication 'Switching System, by R. J.Murphy et al.

(3) U.S. patent application Ser. No. 463,587, tiled June 14, 1965, nowPatent No. 3,413,421 for Identifying Arrangement for CommunicationSwitching Systems, by A. S. Cochran and F. B. Sikorski.

(4) U.S. Patent 3,211,837 issued Oct. 12, 1965, for Line IdentifierArrangement for Communication Switching System, by L. Bruglemans.

(5) U.S. Patent 3,170,041 issued Feb. 16, 1965 for CommunicationSwitching System, by K. K. Spellnes.

References 1 and 2 describe the system in which the invention isincorporated. Reference 3 covers a line identification arrangement forthe terminals of the main switch network of the system, and alsoincludes the description of these terminal circuits. Reference 4describes a line identification arrangement similar to that used in thedial service assistance group of this application. Reference 5 covers aprior switching system and includes a list of several U.S. patentapplications at the end thereof; which are of interest with respect tothe logic circuits, flip-flops, and other building blocks used in thesystem described in the present application.

In describing the apparatus in the system various conventions have beenused. For example, a minus sign adjacent a small circle representing aterminal indicates -50 volt connection from the exchange battery. Aspecific number along with the sign'adjacent a terminal indicates thatvalue of voltage from an electronic power supply, for example -16indicates a negative 16-volt potential connection. The relay circuitsused in the system include both conventional telephone type relays inwhich an armature attracted -by a core actuates a plurality of contactsets, and also relays of the reed type in which the contact sets are insealed reed capsules encircled by the relay winding or windings. Thereis no indication in the present disclosure distinguishing these twotypes of relays since this fact is not pertinent to the invention. Whilethe relays are shown with large numbers of contact sets, in actualpractice slave or parallel connected relays may be used to actuate someof these contacts.

The electronic logic circuitry used in this system is direct-coupled(D.C.), that is, signals are represented by steady-state voltages. Twolevels are employed. The first level is a negative potential, andrepresents the binary one, true, on, or active condition. The secondlevel is ground potential and represents the 'binary zero, false off, orinactive condition. These logic circuits along with nip-flops forcounting and register purposes are used in the various scannersdisclosed herein in block diagram form.

The logical circuits use NOR gates, each of which is a one-transistorlogical element whose output is true if all of the inputs are false, andwhose output is false if any one of the inputs is true` The inputs arecoupled through individual resistors to the base electrode, and theoutput is taken from the collector electrode.

A relay driver is a circuit represented by a triangle having a lineacross it parallel to the base, with a single input to the base, and acontact adjacent to the apex. Each relay driver comprises a singletransistor with the input connection to its base electrode, and awinding in the collector circuit which operates the single contact.

An inverter amplifier is a circuit similar to a NOR gate, except that ithas only a single input. For convenience in the drawings, most of thelogic gate circuits have been represented by AND gates and OR gates. Inactual implementation an AND gate is achieved by using a NOR gate witheach of the inputs inverted, and an OR is obtained by using a NORfollowed by an inverter amplifier. It may be readily seen that insituations in which AND functions and OR functions appear alternately intandem that NOR gates may be used with no inverters between them. A dotor small circle at an input or output designates an inversion or inhibitfunction.

In describing the logical operations performed by the gate circuits,Boolean algebra equations are used. In this notation the addition symbolsignifies OR, the multiplication symbol, expressed or implied, signifiesAND, and overlining signifies the inverted condition.

A test gate is a NOR gate designed to detect a negative input potentialas a true condition and an open connection or ground as a falsecondition, while a regular NOR gate recognizes an open connection ornegative potential as a true condition and ground potential as a falsecondition. A test gate is indicated in the drawings by a T within thegate symbol.

Referring to FIGS. 1 and 2, arranged as shown in FIG. 16, there is showna symbolic diagram of a DSA (dial service assistance) trunk D111connected through a three stage coordinate switching matrix 2, to a linkL101 associated with an operators position P1. The switching network iscontrolled by a marker 1A shown across the bottom of the two sheetscomprising electronic scanners represented by a circle with a pointertherein, relay trees represented by open triangles or Vs, and othercomponents. In these gures the trunk, link, and position circuits haveshown only the circuit apparatus associated with communication with themarker for network 2. The switching network 2 comprises three stages ofcoordinate arrays of crosspoint relays, each crosspoint relay having anoperate or pull winding in series with a diode, a hold winding in serieswith one of its own contacts and five other contacts for respectiveconductors of a switched path. The interstage links have a P conductorseries connecting the pull windings, a C conductor series connecting thehold windings, and ve other switched conductors. Certain of the Pconductors of the network are connected via relay trees to a trunkidentifier in the marker, and the C leads of all of the interstage linksare connected through relay trees to a path control scanner 211 in themarker.

When a call is received at the trunk D111 for extension to an operatorposition it closes a set of contacts to operate a gate relay G viaground received through a set of contacts in the marker. fRelay IG locksvia a set of its own contacts, lead GLK, and a set of contacts to groundin the marker, Another set of contacts of the relay G extends a 16 voltpotential which extends via a resistor and a set of contacts operated inthe normal mode in the marker, via lead TNP, the G relay contacts, andanother resistor to the lead PLA. Each call received at the trunkincludes priority and class of call information for that particular call-via apparatus not shown in FIG. 1. The priority indication opens aconnection as represented by the break contacts between the lead PLA andone of the leads :PRT-PRS in accordance with the priority of the call,and also opens one of the leads between the lead PLA and one of theleads CL1CL5' in accordance with the class of call. The marker via apriority scanner 101 connects ground to one of the ve leads PRF-PRS' inaccordance with the priority to be serviced, and also extends ground viaa class scanner 102 to one of the leads CLT-CLS in accordance with theclass of call to be serviced. This effectively blanks thecall-for-service potential on lead PLA at all trunk circuits exceptthose of the priority and class then being serviced by the marker. Themarker when operating in the normal mode for servicing calls originatingat the trunks first opens the ground connection to lead G so that noadditional trunks can operate their gate relays until all the trun-ksalready calling for service (having their gate relays locked to groundon lead GLK) have been serviced. The priority and class scanners areoperated to service all calls of each priority and class combination,one call at a time. Assuming that these scanners are at the positioncorresponding to the marked indication in trunk D111, the groundpotentials from these two sca'nners is then disconnected from lead PLA.The -16 volt potential extends from lead PLA through the operate windingand series diodes of the A and B stages and appears at lead PBC101extending to the AB group scanner 103 in the trunk identifier. Thepotential is also extended through an OR gate to a call-for-serviceconductor CFS.

T'he trunk identification arrangement including scanners `103, i104 and|105 is of the type covered by the Bruglemans patent, reference 4. Themarker responds to the CFS signal to operate the AB group scanner 103 tofind the calling potential on lead PBC101. This identifies one of ve ABgroups of the switching network. The output of the scanner 103 causesrelay 'trees to operate to connect the P conductors of certain of the ABinterstage link to an A card scanner 104 and also to connect the Cconductors of the BC links associated with that AB group to the pathcontrol scanner 110. The marker then enables the A card scanner whichdetects the calling potential on lead PAB-111, thereby identifying theparticular A matrix. The output of the A card scanner operates relaytrees to connect the PLA leads of that A matrix to the trunk scanner105, and to connect the C conductors of the AB links of that A matrix tothe path control scanner 110. The trunk scanner 105 is then operated toidentify the calling potential appearing on lead PLA111 to therebycomplete the identification of trunk D111. The output of the truntkscanner 105 in conjunction of the A card scanner 104 operates a relaytree to connect lead TP1'11 from trunk D111 to a polar relay TCK inpreparation for eventually establishing the connection in the network.

To find an idle position circuit and link, the marker in the normal modeextends -16 volt potential via a resistor and a set of contacts to leadNPITP connected in multiple to all of the position circuits and thencevia a resistor to a position test conductor PT. Each position includesan arrangement for indicating that it serves certain classes of calls asrst choice, other classes as second choice, and other classes as thirdchoice. There are fifteen conductors connected in multiple to all of thepositions for the class-choice combinations, the first choice conductorsbeing CHAI-CHAS, the second choice conductors being CHBl-CHBS, and thethird choice conductors being CHCl-CHCS. At each position class-choicecornbination the circuit between lead 4PT and the correspondingclass-choice conductor is broken, as represented in I3-IG. 2 by breakcontacts in series with diodes in the individual leads. The choicescanner 212 in the marker connects ground to one of the fifteenconductors. Assuming that position P1 handles the class of call receivedat trunk D111 on a irst choice basis and that the choice scanner 212 isat the corresponding position connecting ground to the corresponding oneof the leads CHA1- OHAS, the -16 volt potential on lead PT extendsthrough normally closed contacts to the position idle test conductorPITl to the position scanner 211. The marker operates this scanner toselect the call at this position. The output of the scanner 211 operatesrelay trees for connecting leads from the link L1 and the other linkcircuits associated with this position; the link idle test lead LIT|101and the corresponding set of test leads from the other links associated-with this position being connected to the path control scanner i110.When the link is idle -16 volt potential via a resistor in the markerand a link idle test potential lead LITP connected in multiple to all ofthe links extends to LIT101.

Coincidence gating means associated with the path control scanner 110now has available information combined from the C leads of the AB linksand the BC links and the LIT test leads of the position links. Themarker causes the path control scanner y110 to operate to select anavailable path. The output of the path control unit in combination withthe output of the position scanner 2-1I1 now operates a relay tree toconnect the lead LPltltl to a polar relay LCK. The marker completes aground connection to the two polar relays TCK and LCK to operate theconnect relays TCN and LCN in the DSA trunk and link respectively. Anoperate path now extends from the negative exchange battery potentialthrough a resistor and a set of contacts in the marker to lead TPH,through contacts of relay TCN to lead PLA, thence in series through thepull windings of the A, B, and C stage crosspoints of the selected path,via contacts of relay LCN to lead LPH and then via a set of contacts inthe marker to ground, thereby operating the three stages of the matrixin series. The path is held via the hold windings of the threecrosspoints in series with a cutol relay in trunk D111 to exchangebattery and ground via a cutoi relay CO in the link L101. The marker isthen released to serve another call.

The marker is also arranged to service calls originating by theoperators at the positions, using a sequence of operation substantiallythe same as that used for servicing calls from the trunks. Whenoperating in the switchboard mode the -16 volt potential at the lead TNPto the trunks and at the lead NPRITP to the positions is disconnected,and instead the potential is connected to lead TMP to the trunks and tolead CPITP to the positions. The principle is to mark all of the idletrunks to make them appear as though they were calling for service, andto mark the position circuits which are calling for service as thoughthey were idle and available for connections. Note that in the trunkcircuit D111, if it is calling for service or if it is busy andtherefore has the cutoff slave relay COS operated, this negativepotential is disconnected from lead PLA. Also if the trunk is busy ithas ground potential via contacts of the cutoff relay CO connected tolead PLA.

The operator initiates a call by operating a key to operate a relay ZCFSwhich then locks by its own contacts and completes a ground connectionto operate a gate relay PGT via ground on lead GP from the marker, thegate relay locking via. its upper winding. The call for service isindicated to the marker via contacts of the gate relay PGT to complete aconnection from --16L volts on the common conductor PCFSP to commonconductor PCFS which produces a signal on lead SCFS in the marker.

The priority scanner 101, class scanner 102, and choice scanner 212 arenot used in the switchboard mode.

The marker now proceeds in substantially the same sequence as describedin a call for the normal mode. The trunk identiiier operates its threescanners to select a trunk having the negative potential on its leadPLA. The position scanner 211 scans for a calling position, which hasextended the negative potential from the marker via lead CPITP andresistor and contacts of the gate relay PGT in series with normallyclosed busy contacts to lead PIT1 and the scanner 211.

The path control scanner now selects an idle path in the same manner asin the normal mode; and the connection is completed also in the samemanner as in the normal mode. The marker is subsequently released toservice other calls.

FIG. 3 is a block diagram of the principal portions of a completeexchange. The DSA (dial service assistance) group at the top of theligure corresponds to the arrangement shown symbolically in FIGS. 1 and2. The exchange also includes a switch group shown in the center of theligure, and a common control group sho-wn at the bottom of the ligure.The switch group comprises a live stage network 22 for connectingtogether any two of a plurality of terminals. These terminals include aplurality of line and trunk circuits Tl-TN of various types, a pluralityof register junctor circuits R11-RIN, and the dial service assistancetrunks D111-D555. Each of the terminal circuits Tl-TN has one networkterminal connection having two appearances, one at the A stage and oneat the C stage. Each of the register junctor circuits has two networkterminals one for receiving and one for sending, each likewise havingboth an A appearance and a C appearance. Each of the DSA trunksD111-D555 has two switch group network terminals, one for frontconnections and one for rear connections, each of these terminals havinglikewise both an A appearance and a C appearance at the network 22. Eachof the DSA trunks D111-D555 also has one terminal appearance at the Astage 2A of the DSA group switching network 2. In addition to the A andC sta-ges, the network 22 includes a BA stage, a BB stage and a BCstage, the entire network being a nonblocking configuration. Connectionsthrough network 22 are controlled by one of the two markers 21A and 21B,these markers being alternately on-line. An allotter 21AL and amaintenance section 21MS is common to the two switch markers 21A and21B.

The common control group includes three common logic units 31A, 31B, and31C, each of which receives and processes all call informationsimultaneously. A parity circuit 33 includes comparison apparatus fordetermining whether all three of the common logic units are inagreement, and for causing appropriate operating and maintenance actionto be taken if they are not in agreement. Memories 32A and 32B areassociated respectively with the common logic units 31A and 31B. Outputinformation is taken only from one of the common logic units 31A or 31Bat any one time. The common control group also includes a coordinateswitching matrix 33 for connecting any one of the register junctors toany one of a plurality of receivers or transceivers Rl-RN. These unitsindividually are arranged for interchange multifrequency receiving andsending or for subscriber touch calling multifrequency signaling. Dialpulse signaling is detected in the register junctor in which case noconnection via matrix 33 is required. Each of the switch terminationsalso has a connection, not shown, to the common control for busyindication.

In the DSA lgroup the dial assistance switchboard DAS has twentypositions P1-P20, and each position has eight links, those associatedwith position P1 being designated L101L801 and those associated withposition 20 being designated Ll-L820. Each link may be connected via thenetwork 2 having the three stages, 2A, 2B and 2C to any one of the DSAtrunks D111-D555. The connections through the network 2 are controlledvia the DSA markers 1A and 1B which are alternately on line. Common'tothe two markers there is an allotter 1AL and a maintenance section 1MS.Only one of the two markers is on line at any one time.

Assume now that a call is received at terminal circuit T1 from asubscriber line to be completed to an operator. All of the terminalcircuits of the switch group are connected in multiple via amulticonductor group 10 to the two switch markers 21A and 21B, and P andC conductors of the interstage links are also connected to the marker ina manner similar to those in the DSA marker 1A. Assuming that marker 21Ais on line, the call is detected and identified via conductors in group10'. The information is forwarded from the marker via a multiconductordata bus to the common logic units of the common control group. Thecommon control then selects an idle register junctor such as R11 and viathe data bus conductors 30 supply the terminal information for terminalsT1 and the receiving terminal of R11 to the marker 21A. The marker thenselects and establishes an idle path between these two terminalslthrough the five stages of network 22 and releases. The common controlgroup connects the junctor R11 via matrix 33 to a local subscriber touchcalling receiver such as R1. The subscriber then transmits signals whichare transmitted from the terminal T1 through the network 22 and thejunctor R11 to the receiver R1. These signals include a designation ofthe priority and an operator class of call. The common logic thenselects a DSA trunk such as D111, obtains the service of a marker 21Aand via conductors of the data bus 30 supplies the designations of theterminals T1 and one of the terminals of trunk D111 along -with thepriority and class information for the call which is stored in themarker 21A. The marker then selects and establishes. a connectionthrough the network 22 from terminal T1 to the terminal of trunk D111,and also via conductors of the group 10 supplies the priority and classinformation to operate relays in the trunk D111.

The trunk D111 now calls for the service of a DSA marker which is online, which we will assume to be marker 1A. The connection is thencompleted in the manner already described with reference to FIGS. l and2.

Since the call for service and trunk identification arrangement betweenthe DSA trunks and the markers 1A and 1B makes use of the switchingnetwork 2, using diodes in series with the pull windings to preventsneak paths via reverse direction of current flow, it is possible toprovide separate paths using a completely separate set of diodes for theconnections to the two markers 1A and 1B. The arrangement of thecoordinate matrices in the switching network 2 is shown in PIG. 4. Thisfigure shows only the pull windings and P conductors, but it is readilyapparent that the other six conductors are always associated therewithas shown in FIG. l.

The network arrangement shown in FIG. 4 serves a maximum of one hundredtwenty-live DSA trunks and twenty positions, each position having twentylinks. There are five AB groups designated AB group l-AB group 5. EachAB group has five (5X4) A matrices and four (5X4) B matrices. Thus eachAB group has ltwenty-five inlets and sixteen outlets. Within each ABgroup each A matrix has a link connecting it to each B matrix. Theselinks are designated by a three digit number designating respectivelylthe AB group, the A matrix in the group, and the B matrix in the group.There are sixteen (5 X10) C matrices, each AB group having a linkconnected to each C matrix. The BC links have a three digit designation,the first digit designating the AB group, and the last two digitsdesignating the C matrix. Likewise the output of the C matrices havethree digit designations7 the first digit designating one of the eightlinks of a position, and the last two digits designating the position.The C matrices are in pairs with the first matrix of each pair servingpositions 1 to 10 and the second serving positions 11 to 20. Thus the Pleads from the outputs of the rst pair of matrices C1 and C2 aredesignated PLP101-PLP120 and those from the last pair C15 and C16 aredesignated PLP801-PLPS20. At the input side of the network the terminalshave three digit designations, designating respectively the AB group,the A matrix within the group, and the input of the A matrix. Thus the Pleads at the terminals of the first A card of the first A group aredesignated PLA111-PLA115, and those of the last matrix of the last groupare designated PLASSl-PLASSS for a total of input terminals.

For call-for-service and AB group identification each marker requires aconnection -to one P lead of a BC link of each AB group. Thereforemarker 1A is connected via the five BC-link P leads, PBC101, PBC201,PBC301, PBC401 and PBCSl; these vbeing the P leads to the first outletof the first B matrix of each AB group. The connections to the marker 1Buse the first outlet of the matrix B4 of each AB group, namely the fiveP leads, PBC113 PBC513.

For the inputs to the A card scanner each marker requires a P leadconnection to one link of each A matrix of each group. Therefore marker1A uses the connection to the P lead of the first output of each Amatrix, and marker 1B uses the P lead of the second outlet of each Amatrix. Thus marker 1A is connected via the twentyfive AB link P leadsPAB111, PAB121-PAB151; PAB211, PAB221-PAB251 etc. up to PABSll-PABSSI.Similarly marker 1B is connected via the twenty-five AB link P leadsPAB112, PAB122PAB152 etc. up to PAB512- PABSSZ. It will be readilyapparent in tracing the connections from the PLA conductors of thetrunks through the network to the P lead connections to the markers thatmarker 1A uses a completely separate set of diodes from those used bymarker 1B. Thus a shorted or open diode in a network can cause troublein only one marker, and the maintenance apparatus can be designed toreadily detect the source of trouble. The parity check arrangement ofFIG. l5 aids in the trouble detection.

DSA TRUNK (FIGS. 5, 6 AND 7) The DSA trunk D111 is shown in FIGS. 5, 6and the left portion of FIG. 7. Only a portion of the apparatus of Athetrunk is shown sufiicient to explain the general operation. Some of therelays have only contact sets shown, in which case the referencecharacter does not have a figure number prefix.

The trunk has three network terminations, two of these shown at ltheleft side of FIG. 6 being the front and rear terminations of the switchnetwork 22, and one shown at the top of FIG. 7 to the DSA network 2.There is also provision for time division signaling via the conductorsS1-S16 of conductor group 15 connected in multiple,-

between all of the DSA trunk circuits as shown in FIG. 5 and all of theposition circuits as shown in FIG, 10. The switch network terminationsare substantially the same as those of the other switch networkterminations as disclosed in references 2 and 3.

An incoming call is received via the rear termination. The switch markergrounds the lead CM-R and places resistance battery on the lead PTG-R tooperate relay GTCR. The operation of relay 6TCR connects severalconductors only part of whichv are shown in FIG. 6 via conductor group10 to the switch marker. The marker places ground on lead TC to operaterelay 6TCSR. The operation of relay TCSR connects additional ones of theconductors via conductor group 10 to the switch marker and operatesrelay SCSRS to connect the leads PRI, PRZ, PR4, PRS, CL1, CL2 and CL4.The switch marker forwards priority and class information via theseconductors as ground signals which operate the corresponding ones of therelays SPRl-SPRS and CL1-5CL4. These relays then lock to store theinformation in the trunk circuit. The switch marker causes theconnection through the switch network to the rear termination to becompleted and it is then released. The cutoi relay 6COR is now operatedin the holding path of the connection, and operates relay 6ORS. Contactsof relay GORS complete a connection from lead G from the DSA markers tothe Vwinding of relay 7G.

When the DSA marker is ready to accept calls it grounds lead G therebyoperating relay 7G. Relay 7G locks to lead GLK, connects lead TNP via aresistor to lead PLA, and connects the priority and class diode tree tothe ve priority leads PRO-PR4 and five class leads CLT-CLS' to the DSAmarker. The priority relays disconnect one of the priority conductors,and the class relays disconnect one of the class conductors from thelead PLA in accordance with the code combination of the relays, namelyfor no priority relays SPR2 and SPRS operate to disconnect lead PRO',for priorities 1, 2 or 4 the corresponding one of the relays SPR1, 5PR2or SPR4 operates to disconnect the corresponding one of the leads PRI',PR2 or PR4'. For priority 3 relays 5PR1 and SPR2 operate to disconnectlead PR3. For class of call information, operation of one of the relays5CL1, 5CL2 or SCL4 opens the connection to the corresponding one of theleads CLI', CL2' or CL4; operation of relays SCLl and 5CL2 opens theconnection to lead CL3', and operation of relays 5CL1 and SCL4 opens theconnection to lead CLS. The marker grounds one of the 5 leads PRO- PR4and one of the class leads CL1-CLS to thereby place ground on lead PLAfor all calling DSA trunk circuits except those having their priorityand class relays operated to indicate the priority and class then lbeingserviced by the marker.

A negative potential on lead TNP via the contacts of relay 7G on leadPLA causes a call for service signal to be extended through the DSAnetwork 2 to lead PBC101 to inform the DSA marker of the call forservice. The DSA ma-rker then identies the calling trunk via thenegative potential on leads PBC101, PAB111 and PLA111. To complete theconnection through the DSA network 2 the marker grounds lead TP111 tooperate the connect relay 7TCN. The marker subsequently places -50 voltpotential on lead TPH which extends through the contacts of relay 7TCNto lead PLA to operate the selected path through the DSA network 2. Acontinuity check is made from lead CCKT through contacts of relay 7TCNto conductor T and also shorting together leads R and T1, and R1 and ECto make the continuity check through the network. Relay 7CO operates inthe hold path of the network. The DSA marker releases, and relay 7COSoperates connecting the leads S1-S9 of the time division signaling group15. The DSA operator is summoned `by a flashing lamp in the associatedlink. The operator answers by operating the appropriate talk key. Timedivision signals via the lead EC through the network and transistor S0operate relay STKO viaconductor S1. The operation of STKO operates relaySTKOS. Relay STKOS operates relay HB and also relay 7SXF via a path notshown. The operation of relay SHB operates relays STLK, STKR, SHBS, andSSCP. The operation of relays STLK and STKR extends the transmissionpath to the operator. The operation of relay SSCP extends the leadsS10-S16 and closes relay SCC. The time division class and prioritysignals are forwarded to the DSA position through the contacts of theoperated class and priority relays and conductors S10-S16. After itsslowto-operate interval, relay SCC operates, locks, and releases relaySSCP.

To extend the call the operator operates the key in the position circuitwhich operates the relay SSF via time division signals. The operation ofrelay SSF releases relay STKR to cut off the calling party, and connectsnegative battery potential to lead CM-F to provide acall for servicesignal to the switch marker via conductor group 10. The switch markerth'en provides a connection from the front termination through theswitch network 22 to a register junctor, in the same manner as describedfor the connection to the rear termination. When the register is readyto accept information, relay 7SXF is used to extend a simplex signal viathe network 2 to light a send pilot lamp. The operator keys in thecalled number with'the first digit being the priority and restores thesend front cutoff rear key, but does not restore the talk key. When thesend front cutoff rear key is restored the time division signal isremoved from lead S2 restoring relay SSF, which operates relay STKR. Theregister processes the call and then drops the register-DSA trunkconnection and establishes a second and nal path from the fronttermination to a switch network terminal.

The operator can change the calling (rear) partys class by keying in anew class to operate various combination of relays SRCA, SRCB and SRCCby time division signals over leads S4, S5 and S6. The operation of oneor more of these relays releases the holding ground of the previouslyoperated class relays, releases relay SCC, and operates relay SCRG.After its slow-to-operate interval, relay SCRG operates and connects aholding ground to the class correeds. When the class keys are restoredat the position, the relays SRCA, SRCB, and/or SRCC restore, releaserelay SCRG, and operate relay SSCP. Relay SSCP extends leads S10 to S16to provide a display of the new class, and operates relay SCC. After itsslow-to-operate interval, relay SCC operates and releases relay SSCP.

After receiving the off hook signal, the operator may disconnect withoutreleasing the link by restoring the associated talk key. This removesthe time division signal from lead EC to cut otf transistor 50. Thisreleases relay STKO, which in turn releases relay STKOS. Relay STKOSrestores and releases relays SCC and STLK. Since the link has not beenreleased, the operator retains complete front and rear supervision. Theoperator may also reenter the transmission facility by operating theassociated talk or monitor key to operate relays STKO, STKOS, and STLK.Relays SSCP and SPC repeat the class and priority cycle.

If the operator desires to release the link upon retiring from the call,the link release key is operated at the associated position. A timedivision signal via lead S4 operates relay SRL which locks at its secondwinding. The operator then restores the associated talk key cutting offtransistor S0 and releasing relays STKO and STKOS, and also releasingthe matrix connection. The release of relays STKOS releases relays STLKand SCC. The release of the matrix connection releases relays 7CO and7COS. Relays 7SXR and 7SXF are operated, thus maintaining the off hooksupervision to the calling and the called party. When the operatordisconnects in this manner, the circuit cannot be reaccessed Ibyoperating the associated talk or monitor key. The associated link hasbeen released and is free to handle subsequent calls. The operator cancancel the link release operation by momentarily operating the sendfront or send rear key. Relays SSF` or SSR momentarily operate openingthe locking winding of relay SRL.

LINK CIRCUIT (FIG. 8)

One of the eight links associated with position P1 is shown in FIG. 8.Each link has the following controls and supervisory lamps at theoperator position: link busy lamp 8B, rear supervisory lamp SR, frontsupervisory lamp 8F, trunk and monitor key STK, and link release keySRK. Since all eight link talk keys are connected in series, only onelink can be accessed at a time.

Each link can be associated with the common position equipment forre-ring, sending, etc. Once `a link is associated with a DSA trunk andthe call extended, the operator can hold or release the link. Theoperator can monitor the

